Process for recovering pyrochlore mineral containing niobium and tantalum

Abstract

Niobium and tantalum containing pyrochlore is recovered from high silicate gangue content ore with good selectivity and yield employing collectors of formula ##STR1## wherein R 1 , R 2 and R 3 are independently 8 to 16 carbon straight or branched chain alkyl groups, at pH 1.5 to 6.5.

I claim: 
     
       1. Process for recovering a concentrate of pyrochlore mineral containing niobium and tantalum from an ore containing pyrochlore mineral particles containing Ta 2  O 5  in a weight ratio of Ta 2  O 5  :Nb 2  O 5  of at least about 0.04:1 and gangue materials, said process comprising the steps of: forming an aqueous pulp of the ore in a small particle size suitable for froth flotation; conditioning the pulp by bringing into admixture therewith (a) a collector selected from the group of monofunctional and difunctional phosphoric acid esters of the formulae ##STR3## and mixtures thereof wherein R 1 , R 2 , and R 3  are independently selected from the group consisting of alkyl groups of about 8 to 16 carbon atoms, in an amount sufficient to collect said pyrochlore present in the pulp to provide a concentrate froth relatively rich in said pyrochlore mineral containing niobium and tantalum, and (b) an acid-reacting compound compatible with said ore, gangue and collector in an amount sufficient to modify the pH of the pulp to a pH in the range about 1.5 to about 6.5; subjecting the conditioned pulp to froth flotation; and recovering a concentrate froth relatively rich in said pyrochlore mineral containing niobium and tantalum. 
     
     
       2. Process as claimed in claim 1 wherein said alkyl groups are of about 10 to 14 carbon atoms. 
     
     
       3. Process as claimed in claim 1 wherein R 1 , R 2 , and R 3  are each straight chain alkyl groups. 
     
     
       4. Process as claimed in claim 3 wherein said straight chain groups are of about 10 to 14 carbon atoms. 
     
     
       5. Process as claimed in claim 1 wherein the collector is a mixture of said compounds of formulae (1) and (2). 
     
     
       6. Process as claimed in claim 1 wherein the acid-reacting compound is a member selected from the group consisting of hydrofluoric acid, fluoride compounds, fluosilicic acid, fluosilicate compounds, oxalic acid, oxalate compounds, and mixtures thereof. 
     
     
       7. Process as claimed in claim 1 wherein the pH is about 3 to 6.5. 
     
     
       8. Process as claimed in claim 7 wherein the pH is about 4 to 6.5. 
     
     
       9. Process as claimed in claim 8 including the step of cleaning the recovered concentrate froth by forming an aqueous pulp therefrom, adding further quantities of said collector and of said acid-reacting compound to reduce the pH to a pH lower than in the first-mentioned froth flotation stage and in the range about 3 to 4, conducting a second froth flotation and recovering a secondary froth concentrate. 
     
     
       10. Process as claimed in claim 9 including cleaning the secondary froth concentrate in a further flotation stage employing said collector and at pH in the range about 2 to 3, and recovering a tertiary froth concentrate. 
     
     
       11. Process as claimed in claim 1 wherein the ore comprises more than about 40% by weight silicate calculated as SiO 2 . 
     
     
       12. Process as claimed in claim 1 wherein the ore contains carbonate and apatite impurities and including subjecting the concentrate froth to leaching with hydrochloric acid to substantially free it of carbonate material and reduce the apatite impurity content, and recovering the leached concentrate. 
     
     
       13. Process as claimed in claim 1 wherein the ore contains magnetic iron-containing impurities and including the step of subjecting the ore to a magnetic separation step employing a relatively low intensity magnetic field and withdrawing the separated-out magnetic components before subjecting the ore to said froth flotation, and subsequently subjecting the concentrate froth, before or after said leaching, to a further magnetic separation step employing a relatively high magnetic field, withdrawing the separated-out magnetic components, and recovering the non-magnetic residue remaining from the further magnetic separation step.